Electricity: Back to basics

Avionics Technology Technician with amp clamp and scope meter. Sometimes you have to check multiple values at the same time. Back to Basics by Jim Sparks Like it or not, aircraft of today are becoming more and more electric. At one time...


Avionics Technology

Electricity

Back to Basics

by Jim Sparks

Like it or not, aircraft of today are becoming more and more electric. At one time calling an electrician was an easy out for resolution of problems with components that involve wires. Many technicians I have worked with over the years have a sound understanding of hydraulic systems but when it comes to devices operating on electrons rather than fluid they feel out of place. Troubleshooting electrical issues is really not that much different than hydraulic problems. Many of the rules are the same. Although electrons move a bit quicker than fluid, and electron leaks are detected by smoke rather than drips.

A pump is a device that converts mechanical energy into fluid movement so a pump installed in a hydraulic system creates the flow and it is the restriction or resistance to fluid movement that causes the pressure increase. In order to take advantage of hydraulic power a specific force or pressure needs to exist in order to move the fluid allowing restrictions to be overcome. This is however, only part of the requirement. Flow and pressure are the two variables and with both of these elements present work can be accomplished. Electrical power is also the result of combining electrical flow and pressure.

Inventors and definitions
Count Alessandro Volta was an Italian physicist and among his credits was the forerunner of the modern battery. This device was built in 1800 and as a result the basic unit of electrical measurement was named in his honor. In fact it is this very unit that is used as a reference for electrical pressure. The formal definition of a volt is joule per coulomb. Simply put this is the potential difference between two points. A pressure gauge employs the same principle. As the pressure being monitored is always referenced as either atmospheric pressure or a second point to illustrate pressure differential.

The ampere is the standard unit of measure for electrical flow and where a hydraulic system may use gallons per minute an ampere is the number of electrons flowing through a conductor in a specific time.

Georg Simon Ohm experimented with early batteries in the early 1800s and based on his observations some very interesting and pertinent conclusions were reached. Ohm noted that the amount of current flow in a wire was directly proportional to the diameter of the conductor and inversely proportional to the wire length. This was the foundation of Ohm’s law, which states the voltage consumed by a device is a result of the amount of current multiplied by the internal resistance of the component.
In other words E = I x R, where E is voltage, I is current, and R is resistance. The relationship of these simple three letters when understood provides the key to solving many of the discrepancies that plague aircraft electrical systems.

One coulomb is the amount of charge accumulated in one second by a current of one ampere. Electricity is actually a flow of charged particles, such as electrons, protons, or ions. The charge on one of these particles is a whole-number multiple of the charge on a single electron, and one coulomb represents a charge of approximately 6.241 506 x 1018 electrons. The coulomb is named for a French physicist, Charles-Augustin de Coulomb, who was the first to measure accurately the forces exerted between electric charges.

Power supply and breakout box Generator shunt attachment
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